NavList:

Lu Abel wrote:

"I ran into an immediate shock:  while we of the mariner persuasion call
the difference between true north and magnetic north "magnetic
variation," most of the rest of the scientific community calls it
"magnetic declination."
For example, see http://en.wikipedia.org/wiki/Magnetic_declination
Does anyone know why this disparity in terminology exists?"

 

I don't know how we ended up with two terms (maybe geologists picked it up from continental usage?), but I do think it's important to be aware that the vast majority of people who know about "variation" call it "declination".

 

I will say this though: the existence of these two terms is proof that two distinct user groups can invent equally BAD technical terminology! Neither of the terms is descriptive and both can easily be confused with other phenomena. Declination sounds more like an alternative name for magnetic dip. Variation sounds more like a term for the rate of change of the magnetic field direction. Oh well. We're stuck with 'em now.